Looking for current and maintained information and documentation on (Linux ) Open Source High Availability HA Clustering?You probably should be reading the Pacemaker site clusterlabs.orgThis site conserves Heartbeat specific stuff. See Site news for details.

Commercial Support

Support for the Linux-HA software is available from a variety of places. The following organizations provide paid support for Linux-HA:

Update: Acutally, today (2015), the only place where you really get support for Heartbeat, or Heartbeat + Pacemaker based clusters is Linbit

Everyone else has already phased out Heartbeat. (Yes, the guy saying so is Heartbeat maintainer and Linbit employee; and my impression may be wrong).
For broader future support, you probably should be considering moving to Corosync 2.x + Pacemaker anyways.
Below is the list as of places where one used to get support for Heartbeat, and where (I think) you still will get support for "Linxu-HA" clusters,
based on Corosync 2.x + Pacemaker.

LINBIT provides 24/7 global support, consulting and training for DRBD, Heartbeat, Pacemaker, Corosync and other HA-software suites. Philipp Reisner and Lars Ellenberg, the authors and maintainers of DRBD, oversee LINBIT's Professional Services team. LINBIT is also the author and maintainer of the DRBD User's Guide.

tummy.com, ltd. has extensive experience with High Availability deployments dating back to 1996, and provides consulting and support for Linux-HA on many Linux platforms. Additionally, they have a true five-nines facility and offer High Availability managed hosting services - includes DRBD

B1 Systems is primarily specialized in Linux Clustering and Virtualization solutions and provides international consulting, training and support services. Also in combination with other Open Source solutions i. e. OCFS, DRBD, Linux Virtual Server (LVS) or HASIv2.

IRC

We are trying to consolidate everything Linux HA Cluster related under the Clusterlabs umbrella now (2015).

If you don't get immediate response, please be patient. Consider that most people in there have day jobs,
may be working on a deadline, or simply are located in different time zones. Just describe your situation,
ask your question, and linger a while. Usually someone will come along and pick it up.

Historically, there have been two more channels, you may find mentioned elsewhere: irc://irc.freenode.org#linux-ha used to be our more Heartbeat stack centric channel,
irc://irc.freenode.org#linux-cluster used to be our more Corosync / RHCS centric channel. To be able to give you a less scattered experience,
we now recommend you to please start out on #clusterlabs, though.

Mailing Lists

Due to the prevelence of SPAM in the internet, ALL our mailing lists require subscribing before you can post to them.
So be sure and subscribe, or don't try and post to them.

Pacemaker related questions

If you want to discuss not heartbeat, but pacemaker/CRM specific questions,
you get better results at the Pacemaker mailing lists.

Announcement Mailing List (announce-only)

The announcement mailing list is a low-traffic announce-only
mailing list where notifications for new releases, major bugs, etc. are sent.
We strongly recommend that everyone using or redistributing the Linux-HA software subscribe
to this list.